This invention relates to a hydraulic torque impulse mechanism which is intended for a torque delivering tool and which includes a rotatively driven drive member provided with a concentric fluid chamber as well as a radially acting cam means, an output shaft extending into the drive member fluid chamber and having two radially extending cylinder bores, which communicate continuously with each other via a central high pressure chamber, and two oppositely disposed piston elements reciprocable in the cylinder bores by the cam means.
Impulse mechanisms of the above type, disclosed for example in U.S. Pat. No. 5,092,410, are characterized by a very efficient impulse generation, because the high pressure chamber is very small and the fluid entrapped therein at impulse generation is compressed simultaneously from two opposite directions. This makes the pressurized fluid volume very stiff, and because of this high stiffness, the pressure build-up and the retardation of the drive member takes place very abruptly at each impulse generation.
Accordingly, the resulting torque impulses have an extremely steep characteristic. This is a drawback when providing the tool with a torque transducer for producing electric signals reflecting the torque magnitude of the delivered impulses. The very steep impulse characteristics makes it difficult to obtain reliable signals from the torque transducer.